好的，所以这就是问题所在：
我正在制作一个随机生成地形的游戏。地形生成一次并保存到磁盘/ SD卡。它做得非常好：）
要做到这一点，我运行一个SplashScreenActivity来运行我的开始启动画面，世界创建或世界加载，具体取决于它的启动方式。 实际的程序生成是使用4D Simplex Noise完成的，使用由Stefan Gustavson编写的类，由Peter Eastman编写（并由我自己优化和加速至少50％，将变量拉出来并使它们变得静止......但问题是我即将描述在这些变化之前发生的事情。
基本上我使用他们的噪音功能来填充有噪音的瓷砖。在我的世界创建循环中，我循环遍历所有像素，每个图块遍历所有像素，调用类的SimplexNoise4D.noise（x，y，z，w）函数来填充每个像素（我正在计划发送类的xyzw-pixel-collection集合，因此它可以运行该方法以便更快地访问。）
无论如何，这一切都很有效。但是当我退出游戏活动并返回主菜单时，如果我再次尝试运行世界创建，则访问SimplexNoise类方法（.noise方法及其使用的内部方法）是缓慢的！ 使调用以正常速度运行的唯一方法是退出整个应用程序（使用任务管理器终止它）并重新启动应用程序。然后，第一次运行它时，平铺创建速度应尽可能快。 使用调试/方法profilling等，似乎对.noise方法的调用以及对dot方法的调用在第二次尝试运行整个世界创建时花费了大量时间。
所以，再次，我第一次使用SimplexNoise.noise（xyzw）进行循环访问，它运行正常。然后第二次访问所有图块中的所有像素（在游戏之后），并且对该类的所有方法调用都需要FOREVER。
有谁知道为什么会发生这种情况以及如何阻止它发生？
CNC中 只是为了清理，应用程序的工作方式如下： mainmenuActivity - ＆gt; chooseWorldSizeActivity-＆gt; Splashscreen，通过大量调用SimplexNoise.noise（xywz）创建世界 - ＆gt;退出splashscreen-＆gt;开始游戏活动。
这很好，而且速度很快。 但是，如果我退出gameActivity（进入主菜单），然后 - > gt; selectWordlSizeActivity-＆gt; splashscreenActivity，现在对SimplexNoise.noise（xyzw）的调用将永远完成。 如果我停止整个应用程序（使用atskkiller），则世界创建需要正常时间再次运行。我无法找到原因！ - /编辑 -
调用循环（在ASyncTask的doInBackground（）中）就是：
for(loop over rows of tiles)
for(loop over column tiles)
for(each pixel)
create x, y, z, w;
SimplexNoise.noise(xyzw);
Simplex Noise类如下所示：
`
public final class SimplexNoise4D { // Simplex noise in 2D, 3D and 4D
private static final Grad grad3[] = {new Grad(1,1,0),new Grad(-1,1,0),new Grad(1,-1,0),new Grad(-1,-1,0),
new Grad(1,0,1),new Grad(-1,0,1),new Grad(1,0,-1),new Grad(-1,0,-1),
new Grad(0,1,1),new Grad(0,-1,1),new Grad(0,1,-1),new Grad(0,-1,-1)};
private static final Grad grad4[]= {new Grad(0,1,1,1),new Grad(0,1,1,-1),new Grad(0,1,-1,1),new Grad(0,1,-1,-1),
new Grad(0,-1,1,1),new Grad(0,-1,1,-1),new Grad(0,-1,-1,1),new Grad(0,-1,-1,-1),
new Grad(1,0,1,1),new Grad(1,0,1,-1),new Grad(1,0,-1,1),new Grad(1,0,-1,-1),
new Grad(-1,0,1,1),new Grad(-1,0,1,-1),new Grad(-1,0,-1,1),new Grad(-1,0,-1,-1),
new Grad(1,1,0,1),new Grad(1,1,0,-1),new Grad(1,-1,0,1),new Grad(1,-1,0,-1),
new Grad(-1,1,0,1),new Grad(-1,1,0,-1),new Grad(-1,-1,0,1),new Grad(-1,-1,0,-1),
new Grad(1,1,1,0),new Grad(1,1,-1,0),new Grad(1,-1,1,0),new Grad(1,-1,-1,0),
new Grad(-1,1,1,0),new Grad(-1,1,-1,0),new Grad(-1,-1,1,0),new Grad(-1,-1,-1,0)};
private static final short p[] = {151,160,137,91,90,15,
131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180};
// To remove the need for index wrapping, double the permutation table length
private static short perm[] = new short[512];
private static short permMod12[] = new short[512];
static {
for(int i=0; i<512; i++)
{
perm[i]=p[i & 255];
permMod12[i] = (short)(perm[i] % 12);
}
}
// Skewing and unskewing factors for 2, 3, and 4 dimensions
private static final double F2 = 0.5*(Math.sqrt(3.0)-1.0);
private static final double G2 = (3.0-Math.sqrt(3.0))/6.0;
private static final double F3 = 1.0/3.0;
private static final double G3 = 1.0/6.0;
private static final double F4 = (Math.sqrt(5.0)-1.0)/4.0;
private static final double G4 = (5.0-Math.sqrt(5.0))/20.0;
// This method is a *lot* faster than using (int)Math.floor(x)
private static int fastfloor(double x) {
int xi = (int)x;
return x<xi ? xi-1 : xi;
}
private static double dot(Grad g, double x, double y) {
return g.x*x + g.y*y; }
private static double dot(Grad g, double x, double y, double z) {
return g.x*x + g.y*y + g.z*z; }
private static double dot(Grad g, double x, double y, double z, double w) {
return g.x*x + g.y*y + g.z*z + g.w*w; }
private static double n0, n1, n2, n3, n4; // Noise contributions from the five corners
private static double s;// Factor for 4D skewing
private static int i;
private static int j;
private static int k;
private static int l;
private static double t; // Factor for 4D unskewing
private static double X0; // Unskew the cell origin back to (x,y,z,w) space
private static double Y0;
private static double Z0;
private static double W0;
private static double x0; // The x,y,z,w distances from the cell origin
private static double y0;
private static double z0;
private static double w0;
private static int rankx;
private static int ranky;
private static int rankz;
private static int rankw;
private static int i1, j1, k1, l1; // The integer offsets for the second simplex corner
private static int i2, j2, k2, l2; // The integer offsets for the third simplex corner
private static int i3, j3, k3, l3; // The integer offsets for the fourth simplex corner
private static double x1; // Offsets for second corner in (x,y,z,w) coords
private static double y1;
private static double z1;
private static double w1;
private static double x2; // Offsets for third corner in (x,y,z,w) coords
private static double y2;
private static double z2;
private static double w2;
private static double x3; // Offsets for fourth corner in (x,y,z,w) coords
private static double y3;
private static double z3;
private static double w3;
private static double x4; // Offsets for last corner in (x,y,z,w) coords
private static double y4;
private static double z4;
private static double w4;
// Work out the hashed gradient indices of the five simplex corners
private static int ii;
private static int jj;
private static int kk;
private static int ll;
private static int gi0;
private static int gi1;
private static int gi2;
private static int gi3;
private static int gi4;
private static double t0;
private static double t1;
private static double t2;
private static double t3;
private static double t4;
// 4D simplex noise, better simplex rank ordering method 2012-03-09
public static double noise(double x, double y, double z, double w) {
////double n0, n1, n2, n3, n4; // Noise contributions from the five corners
// Skew the (x,y,z,w) space to determine which cell of 24 simplices we're in
////double s = (x + y + z + w) * F4; // Factor for 4D skewing
s = (x + y + z + w) * F4; // Factor for 4D skewing
/*int i = fastfloor(x + s);
int j = fastfloor(y + s);
int k = fastfloor(z + s);
int l = fastfloor(w + s);
double t = (i + j + k + l) * G4; // Factor for 4D unskewing
double X0 = i - t; // Unskew the cell origin back to (x,y,z,w) space
double Y0 = j - t;
double Z0 = k - t;
double W0 = l - t;
double x0 = x - X0; // The x,y,z,w distances from the cell origin
double y0 = y - Y0;
double z0 = z - Z0;
double w0 = w - W0;*/
i = fastfloor(x + s);
j = fastfloor(y + s);
k = fastfloor(z + s);
l = fastfloor(w + s);
t = (i + j + k + l) * G4; // Factor for 4D unskewing
X0 = i - t; // Unskew the cell origin back to (x,y,z,w) space
Y0 = j - t;
Z0 = k - t;
W0 = l - t;
x0 = x - X0; // The x,y,z,w distances from the cell origin
y0 = y - Y0;
z0 = z - Z0;
w0 = w - W0;
// For the 4D case, the simplex is a 4D shape I won't even try to describe.
// To find out which of the 24 possible simplices we're in, we need to
// determine the magnitude ordering of x0, y0, z0 and w0.
// Six pair-wise comparisons are performed between each possible pair
// of the four coordinates, and the results are used to rank the numbers.
/*int rankx = 0;
int ranky = 0;
int rankz = 0;
int rankw = 0;
if(x0 > y0) rankx++; else ranky++;
if(x0 > z0) rankx++; else rankz++;
if(x0 > w0) rankx++; else rankw++;
if(y0 > z0) ranky++; else rankz++;
if(y0 > w0) ranky++; else rankw++;
if(z0 > w0) rankz++; else rankw++;
int i1, j1, k1, l1; // The integer offsets for the second simplex corner
int i2, j2, k2, l2; // The integer offsets for the third simplex corner
int i3, j3, k3, l3; // The integer offsets for the fourth simplex corner*/
rankx = 0;
ranky = 0;
rankz = 0;
rankw = 0;
if(x0 > y0) rankx++; else ranky++;
if(x0 > z0) rankx++; else rankz++;
if(x0 > w0) rankx++; else rankw++;
if(y0 > z0) ranky++; else rankz++;
if(y0 > w0) ranky++; else rankw++;
if(z0 > w0) rankz++; else rankw++;
// simplex[c] is a 4-vector with the numbers 0, 1, 2 and 3 in some order.
// Many values of c will never occur, since e.g. x>y>z>w makes x<z, y<w and x<w
// impossible. Only the 24 indices which have non-zero entries make any sense.
// We use a thresholding to set the coordinates in turn from the largest magnitude.
// Rank 3 denotes the largest coordinate.
i1 = rankx >= 3 ? 1 : 0;
j1 = ranky >= 3 ? 1 : 0;
k1 = rankz >= 3 ? 1 : 0;
l1 = rankw >= 3 ? 1 : 0;
// Rank 2 denotes the second largest coordinate.
i2 = rankx >= 2 ? 1 : 0;
j2 = ranky >= 2 ? 1 : 0;
k2 = rankz >= 2 ? 1 : 0;
l2 = rankw >= 2 ? 1 : 0;
// Rank 1 denotes the second smallest coordinate.
i3 = rankx >= 1 ? 1 : 0;
j3 = ranky >= 1 ? 1 : 0;
k3 = rankz >= 1 ? 1 : 0;
l3 = rankw >= 1 ? 1 : 0;
// The fifth corner has all coordinate offsets = 1, so no need to compute that.
/*double x1 = x0 - i1 + G4; // Offsets for second corner in (x,y,z,w) coords
double y1 = y0 - j1 + G4;
double z1 = z0 - k1 + G4;
double w1 = w0 - l1 + G4;
double x2 = x0 - i2 + 2.0*G4; // Offsets for third corner in (x,y,z,w) coords
double y2 = y0 - j2 + 2.0*G4;
double z2 = z0 - k2 + 2.0*G4;
double w2 = w0 - l2 + 2.0*G4;
double x3 = x0 - i3 + 3.0*G4; // Offsets for fourth corner in (x,y,z,w) coords
double y3 = y0 - j3 + 3.0*G4;
double z3 = z0 - k3 + 3.0*G4;
double w3 = w0 - l3 + 3.0*G4;
double x4 = x0 - 1.0 + 4.0*G4; // Offsets for last corner in (x,y,z,w) coords
double y4 = y0 - 1.0 + 4.0*G4;
double z4 = z0 - 1.0 + 4.0*G4;
double w4 = w0 - 1.0 + 4.0*G4;
// Work out the hashed gradient indices of the five simplex corners
int ii = i & 255;
int jj = j & 255;
int kk = k & 255;
int ll = l & 255;
int gi0 = perm[ii+perm[jj+perm[kk+perm[ll]]]] % 32;
int gi1 = perm[ii+i1+perm[jj+j1+perm[kk+k1+perm[ll+l1]]]] % 32;
int gi2 = perm[ii+i2+perm[jj+j2+perm[kk+k2+perm[ll+l2]]]] % 32;
int gi3 = perm[ii+i3+perm[jj+j3+perm[kk+k3+perm[ll+l3]]]] % 32;
int gi4 = perm[ii+1+perm[jj+1+perm[kk+1+perm[ll+1]]]] % 32;*/
x1 = x0 - i1 + G4; // Offsets for second corner in (x,y,z,w) coords
y1 = y0 - j1 + G4;
z1 = z0 - k1 + G4;
w1 = w0 - l1 + G4;
x2 = x0 - i2 + 2.0*G4; // Offsets for third corner in (x,y,z,w) coords
y2 = y0 - j2 + 2.0*G4;
z2 = z0 - k2 + 2.0*G4;
w2 = w0 - l2 + 2.0*G4;
x3 = x0 - i3 + 3.0*G4; // Offsets for fourth corner in (x,y,z,w) coords
y3 = y0 - j3 + 3.0*G4;
z3 = z0 - k3 + 3.0*G4;
w3 = w0 - l3 + 3.0*G4;
x4 = x0 - 1.0 + 4.0*G4; // Offsets for last corner in (x,y,z,w) coords
y4 = y0 - 1.0 + 4.0*G4;
z4 = z0 - 1.0 + 4.0*G4;
w4 = w0 - 1.0 + 4.0*G4;
// Work out the hashed gradient indices of the five simplex corners
ii = i & 255;
jj = j & 255;
kk = k & 255;
ll = l & 255;
gi0 = perm[ii+perm[jj+perm[kk+perm[ll]]]] % 32;
gi1 = perm[ii+i1+perm[jj+j1+perm[kk+k1+perm[ll+l1]]]] % 32;
gi2 = perm[ii+i2+perm[jj+j2+perm[kk+k2+perm[ll+l2]]]] % 32;
gi3 = perm[ii+i3+perm[jj+j3+perm[kk+k3+perm[ll+l3]]]] % 32;
gi4 = perm[ii+1+perm[jj+1+perm[kk+1+perm[ll+1]]]] % 32;
// Calculate the contribution from the five corners
/*double t0 = 0.6 - x0*x0 - y0*y0 - z0*z0 - w0*w0;
if(t0<0) n0 = 0.0;
else {
t0 *= t0;
n0 = t0 * t0 * dot(grad4[gi0], x0, y0, z0, w0);
}
double t1 = 0.6 - x1*x1 - y1*y1 - z1*z1 - w1*w1;
if(t1<0) n1 = 0.0;
else {
t1 *= t1;
n1 = t1 * t1 * dot(grad4[gi1], x1, y1, z1, w1);
}
double t2 = 0.6 - x2*x2 - y2*y2 - z2*z2 - w2*w2;
if(t2<0) n2 = 0.0;
else {
t2 *= t2;
n2 = t2 * t2 * dot(grad4[gi2], x2, y2, z2, w2);
}
double t3 = 0.6 - x3*x3 - y3*y3 - z3*z3 - w3*w3;
if(t3<0) n3 = 0.0;
else {
t3 *= t3;
n3 = t3 * t3 * dot(grad4[gi3], x3, y3, z3, w3);
}
double t4 = 0.6 - x4*x4 - y4*y4 - z4*z4 - w4*w4;
if(t4<0) n4 = 0.0;
else {
t4 *= t4;
n4 = t4 * t4 * dot(grad4[gi4], x4, y4, z4, w4);
}*/
t0 = 0.6 - x0*x0 - y0*y0 - z0*z0 - w0*w0;
if(t0<0) n0 = 0.0;
else {
t0 *= t0;
n0 = t0 * t0 * dot(grad4[gi0], x0, y0, z0, w0);
}
t1 = 0.6 - x1*x1 - y1*y1 - z1*z1 - w1*w1;
if(t1<0) n1 = 0.0;
else {
t1 *= t1;
n1 = t1 * t1 * dot(grad4[gi1], x1, y1, z1, w1);
}
t2 = 0.6 - x2*x2 - y2*y2 - z2*z2 - w2*w2;
if(t2<0) n2 = 0.0;
else {
t2 *= t2;
n2 = t2 * t2 * dot(grad4[gi2], x2, y2, z2, w2);
}
t3 = 0.6 - x3*x3 - y3*y3 - z3*z3 - w3*w3;
if(t3<0) n3 = 0.0;
else {
t3 *= t3;
n3 = t3 * t3 * dot(grad4[gi3], x3, y3, z3, w3);
}
t4 = 0.6 - x4*x4 - y4*y4 - z4*z4 - w4*w4;
if(t4<0) n4 = 0.0;
else {
t4 *= t4;
n4 = t4 * t4 * dot(grad4[gi4], x4, y4, z4, w4);
}
// Sum up and scale the result to cover the range [-1,1]
return 27.0 * (n0 + n1 + n2 + n3 + n4);
}
// Inner class to speed up gradient computations
// (array access is a lot slower than member access)
private static class Grad
{
double x, y, z, w;
Grad(double x, double y, double z)
{
this.x = x;
this.y = y;
this.z = z;
}
Grad(double x, double y, double z, double w)
{
this.x = x;
this.y = y;
this.z = z;
this.w = w;
}
}
}
`